MissoulaAvalanche.org

Avalanche Information for West Central Montana

February 15, 2013 Avalanche Advisory

Current Danger Rating is MODERATE

The avalanche danger in the west central Montana backcountry is MODERATE. It is possible to trigger avalanches on slopes above 7000 feet and steeper than 35 degrees.  The area received just enough snow with plenty of wind to keep the rating at MODERATE. Exposed ridges at higher elevations may have pockets with wind slabs. Winds may have side-loaded gullies and couloirs at higher elevations. A second avalanche problem is loose, surface snow avalanches (sluffs) on very steep terrain; again at higher elevations.

Good Morning! This is Dudley Improta with the West Central Montana Avalanche Center’s avalanche advisory for Friday, February 15, 2013.

Weather and Snowpack Analysis

Mountain temperatures are in the 20’s this morning with winds averaging 10mph, generally out of the west.  The weather system that passed through Tuesday and Wednesday left a few inches and generated high winds.  The winds left us with the possibility of wind slabs at higher elevations (7000 feet and above). A second problem to consider is loose snow sluffs on colder aspects. These sluffs or loose snow avalanches will only occur on very steep terrain.

Tim and I found mostly stable conditions in the Rattlesnake. All aspects were wind affected on the ridges. Cloud cover made for some very nice skiing and riding conditions.

Steve rode up to Hoodoo Pass with Jim Ward.  Along with the wind slab and loose snow situation, they found some deeper layers still showing high quality shears in their snow tests. They did not find any of these layers willing to propagate with further investigation. Hoodoo Pass Snow Profile

Near Lookout Pass, observer Dan Frigard had some lingering concern with deeper layers showing up in his tests, but again no propagation with further testing. The main avalanche problem near Lookout is the wind-loading.

On Tuesday I mentioned that Lost Trail, and the southern Bitterroots, received more snow than the rest of the advisory area during last weekend’s storm; and that snow was sitting on a weak surface.  David Fox found that layer still failing easily, but not propagating. The potential is there for this layer to produce small soft slab avalanches on steep terrain. Lost Trail Snow Profile

We also got reports this week from Seeley Lake (Seeley Lake Snow Profile), Yurtski in the southern Swans and Downing Mountain Lodge near Hamilton. These reports all indicated MODERATE danger associated mainly with the winds.

The Bottom Line

We have very good riding and skiing conditions out there.  It would be easy to ski or ride a few lines and move to steeper terrain and figure nothing is going to happen.  The avalanche problems I mentioned above are hiding in very specific places. And, yes, the older layers are not propagating in testing, but they are showing up.

So, if you are turning up the terrain this weekend; don’t let down on your protocol (risk reduction rituals); one at a time and so forth. Enjoy the winter backcountry; but anticipate the possibility of an avalanche on steep terrain. Check your slopes carefully for terrain traps (anything that increases the danger of being caught in an avalanche) before riding or skiing.

Weather Forecast and Avalanche Outlook

Light snow is predicted to linger today.  A quick ridge of high pressure should develop and cause inversions (a bit warmer at high elevations). This high pressure is supposed to break down quickly and make way for potential mountain snow beginning Saturday night through Sunday. Increased winds are expected with this transition.

What can I say? I know I sound like a broken record; accumulations of snow accompanied by winds. Avalanche danger should remain at MODERATE or slightly increase.

Ski and ride safe and have a great holiday weekend!

If you would like to report on avalanche or snow conditions use our public observations form or send us a note at info@missoulaavalanche.org .

I will issue the next advisory Tuesday February 19.

This information is the sole responsibility of the Forest Service and does not apply to operating ski areas. The avalanche danger rating expires at midnight tonight but you can use the information we provide to help you make more informed decisions regarding travel in avalanche terrain for the next few days.

Our advisory area includes the Bitterroot Mountains from Lost Trail Pass North to Hoodoo Pass, the Rattlesnake Mountains and the Southern Swan and Mission Mountains near Seeley Lake. Avalanche information for the Lookout Pass/St. Regis Basin is available from the Idaho Panhandle Avalanche Center.